1. Field of the Invention
The present invention generally relates to best-effort bandwidth allocating methods and devices, and more specifically, to a best-effort bandwidth allocating method and device whereby, in a case where a best-effort bandwidth in a layer 2 network impartially allocated to each of end users or minimum bandwidth guarantee service is provided in a network of a communication carrier, the best-effort bandwidth is allocated based on a contract money of each of the end users.
2. Description of the Related Art
Conventionally, in Wide Area Ethernet® communications, a minimum bandwidth guarantee type service wherein a contract bandwidth is allocated to an end user (hereinafter, “user”) has been a main communication service. However, in an ATM (Asynchronous Transfer Mode) communications environment, in addition to the minimum bandwidth guarantee type service, there is a bandwidth guarantee and best-effort service where the minimum bandwidth guarantee type service and the best-effort bandwidth type service are combined. Hence, there is demand to perform this bandwidth guarantee and best-effort service in Wide Area Ethernet (registered trademark) communications.
In a case where the bandwidth guarantee and best-effort service is performed in the Wide Area Ethernet (registered trademark) communications, it is a problem that the best-effort bandwidth greater than the bandwidth guarantee may not be impartially allocated to each of the users. The reason why the best-effort bandwidth greater than the bandwidth guarantee may not be impartially allocated to each of the users is that the packet data of a specific heavy user, namely a user sending more data, can easily surpass the best-effort bandwidth.
A method for impartially allocating best-effort bandwidth in a layer 3 network is discussed in, for example, Japanese Laid-Open Patent Application Publication No. 2002-261814, and others.
The method discussed in Japanese Laid-Open Patent Application Publication No. 2002-261814 is a priority control method. That is, CTR (Committed Target Rate) and PTR (Peak Target Rat) are used as parameters in an edge router and an average rate of data traffic sent by the user is measured. Based on the average rate, data of the user less than the CTR are marked in green; data of the user equal to or greater than the CTR but less than the PTR are marked in yellow; and data of the user equal to or greater than the PTR are marked in red. The data are discarded in a core router based on a discard ratio corresponding to each of the markings.
In a case of the minimum bandwidth guarantee transferring service, in order to ease partiality of excess bandwidth allocation due to the difference of the flow numbers, the flow number multiplexed for an event profile is measured and a threshold value such as the CTR (Committed Target Rate) is changed based on a ratio of the inverse of the measured flow number.
The characteristic in the bandwidth guarantee and best-effort service, where the packet data of the user sending more data more can easily surpass the best-effort bandwidth, is discussed with reference to FIG. 1. Here, FIG. 1 is a view showing an output rate of a related art bandwidth guarantee and best-effort service. The bandwidth guarantee is a CIR (Committed Information Rate). The best-effort bandwidth is balanced between the PIR (Peak Information Rate) and the CIR (Committed Information Rate), namely “PIR-CIR”.
As shown in FIG. 1(a), it is assumed that the CIR (Committed Information Rate) and the PIR (Peak Information Rate) of each of the users A, B, and C is the same as the others; and each of the users A, B, and C makes a contract where the CIR (Committed Information Rate) is 5 Mbps and the PIR (Peak Information Rate) is 10 Mbps with a communications carrier. In other words, the minimum bandwidth guarantee rate of each of the users A, B, and C is the same as the others; and the useable bandwidth of the best-effort service of each of the users A, B, and C is the same as the others.
It is assume that data are sent from the user A (port #1) at 8 Mbps; data are sent from the user B (port #2) at 10 Mbps; and data are sent from the user C (port #3) at 7 Mbps; so that these data are gathered and data are output from the port #4 at 20 Mbps. The input rate of all of the data is 25 (=8+10+7) Mbps and data of 5 (=25−20) Mbps are discarded by a shaper function.
Packet data passing without being discarded by the shaper function of the port #4 are processed in the arriving order so as to be output. Therefore, an output rate of the user A is 6.4 Mbps (=8 Mbps×(20 Mbps÷25 Mbps)); an output rate of the user B is 8 Mbps (=10 Mbps×(20 Mbps÷25 Mbps)); and an output rate of the user C is 5.6 Mbps (=7 Mbps×(20 Mbps÷25 Mbps)). See FIG. 1(b).
Since each of the users A, B, and C pays the same amount of contract money under the same conditions for the CIR (Committed Information Rate) and the PIR (Peak Information Rate), the best-effort bandwidth of each of the users A, B, and C should be the same 6.66 Mbps. However, the user sending out the most data can use the best-effort bandwidth more than the user A and the user C. Hence, partiality in that the user sending the most data can use the bandwidth more may be generated.
Furthermore, in the related art impartial control of bandwidth allocation discussed in Japanese Laid-Open Patent Application Publication No. 2002-261814, bandwidth allocation is controlled based on the result of measurement of the arrived number of packets (TCP flow number) for a micro time period such as a Time Sliding Window. Hence, if the data traffic communication ratio of each of the users is measured at a span such as one month that is an accounting subject time period, the best effort bandwidth is not impartially distributed to the users even if the contents of contracts of the users are the same.